The present invention relates to a process for effecting the decontamination, or hydrorefining, of petroleum crude oil, heavy vacuum gas oil, crude tower bottoms, tar sands oil, coal oil extracts, vacuum tower bottoms product, visbreaker product effluent, heavy cycle stocks, and other high-boiling hydrocarbon fractions and/or distillates commonly referred to in the petroleum art as "black oils." More specifically, the present invention is directed toward a catalytic, slurry-type process for hydrorefining heavy hydrocarbonaceous material severely contaminated by the inclusion of excessive quantities of deleterious substances.
In one of its embodiments, the present invention involves a process for effecting the decontamination, or hydrorefining, of a heavy hydrocarbon charge stock for the primary purpose of effecting the destructive removal of a significant amount of nitrogenous and sulfurous compounds, and particularly for the conversion of the insoluble asphaltenic portion of such charge stock into useful soluble hydrocarbon products. Crude petroleum oil, and other heavy hydrocarbon fractions and/or distillates, which boil at temperatures above the gasoline and middle-distillate boiling ranges, generally contain nitrogenous and sulfurous compounds in large quantities. In addition, these high-boiling black oils contain metallic contaminants which exhibit the tendency to exert detrimental effects upon any catalytic composite which may be utilized in a process to which the crude oil, or portion thereof, is subjected. The more common of such metallic contaminants are nickel and vanadium, although other metals including iron, lead, arsenic, copper, etc., may be present. Although the metallic contaminants may exist in a variety of forms, they are usually found as organo-metallic compounds of high molecular weight, such as metal porphyrins and various derivatives thereof. Notwithstanding that the total concentration of these metallic contaminants is relatively small, often less than about 10 ppm, calculated as the elemental metal, subsequent processing techniques are adversely affected thereby. For example, when a hydrocarbon charge stock containing metals in excess of about 10 ppm by weight is subjected to a cracking process for the purpose of producing lower-boiling, normally liquid hydrocarbons, the metals become deposited upon the catalyst employed, steadily increasing in quantity until such time as the composition thereof is changed to the extent that undesirable results are obtained.
In addition to the contaminating influences exemplified by nitrogenous and sulfurous compounds, and organo-metallic complexes, crude oils and other heavy hydrocarbon fractions generally consist of a significant quantity of high-boiling insoluble asphaltenic material. For example, a full boiling range Wyoming sour crude oil, having a gravity of 23.2 API at 60.degree. F., not only is contaminated by about 2.8% by weight of sulfur, approximately 2,700 ppm of total nitrogen, a total of about 100 ppm of metallic porphyrins (computed as elemental nickel and vanadium), but contains a heptane-insoluble asphaltenic fraction in an amount of about 8.4% by weight. Similarly, crude tower bottoms product, having a gravity API at 60.degree. F., of 14.3, is contaminated by the presence of about 3.0% by weight of sulfur, 3,800 ppm of total nitrogen, about 85 ppm of total metals and about 10.9% by weight of asphaltenic compounds. A much more difficult charge stock to convert into valuable, normally liquid hydrocarbons, is a vacuum tower bottoms product having a gravity/API at 60.degree. F., of 7.0, and containing more than 6,000 ppm, of nitrogen, about 4.0% by weight of sulfur, over 450 ppm of metallic contaminants, and about 24.0% by weight of pentane-insoluble asphaltenic material. Asphaltenic material consists of high molecular weight hydrocarbons which are considered to be coke-precursors having the tendency to become immediately deposited within the reaction zone and other process equipment, and on to the catalytic composite in the form of a gummy hydrocarbonaceous residue which effectively deactivates the catalyst with respect to its ability to perform the removal of sulfur and nitrogen by conversion thereof to hydrogen sulfide, ammonia and hydrocarbons. Furthermore, this in effect constitutes a large loss of charge stock and it is economically desirable to convert such asphaltenes into pentane-soluble liquid hydrocarbon products.